A rare earth-iron alloy of neodymium-iron with intrinsic room temperature coercivity exceeding 5 kOe was obtained by Croat, U.S. Pat. No. 4,496,395, assigned to the assignee of this application. A samarium-iron alloy having typically about 40 atomic percent samarium was also disclosed.
U.S. Pat. No. 4,969,961 to Pinkerton et al, assigned to the assignee of the present invention, discloses a magnetically hard compound having the approximate formula SmFe.sub.10 V.sub.2 which exhibits an intrinsic room temperature coercivity of about 5 kOe.
Recently, it has been discovered that interstitial nitrides can be prepared from the R.sub.2 Fe.sub.17 series of rare earth-iron alloys, and that nitriding produces an increase in Curie temperatures. Sm.sub.2 Fe.sub.17 is a member of this rare-earth series.
Two different approaches have been reported for magnetically hardening an Sm-Fe precursor. The first is fabrication of a nitrided, magnetically aligned, metal-bonded magnet using Zn or a similar low melting point metal as the binder. The Sm-Fe-N-Zn pellet so produced has an intrinsic room temperature coercivity H.sub.ci of about 6 kOe. Higher coercivity has been obtained by mechanical alloying of Sm and Fe, nitriding and then cold pressing or resin bonding.
It is desirable to have an improved, economical method for producing magnetically hard Sm-Fe-N compositions.